1. Field of the Invention
The present invention relates to an improvement in a feed unit apparatus in which a feed screw apparatus and a linear guide apparatus are integrally formed.
2. Description of the Prior Art
In an apparatus for accurately moving a movable member relative to a stationary member in an axial direction, it is preferable to constitute the apparatus by combining a feed screw apparatus with a linear guide apparatus. However, since these apparatuses are manufactured entirely separately, in combining these apparatuses, a movement axis line of a nut due to a feed screw and a movement axis line of the nut guided by a guide rail of a linear guide must be aligned. Accordingly, there exists a problem in that a troublesome adjustment is needed in assembling both the apparatuses. For this reason, it has been proposed to constitute a feed unit apparatus by integrating the feed screw apparatus with the linear guide apparatus to facilitate the use.
For example, as shown in FIG. 2 in Japanese Utility Model Laid-Open Publication No. 61-61362, a recess of a trapezoidal shape is formed in a lower part of a nut of a ball screw, and axial ball rolling grooves are formed in the recess. The nut is fitted through balls on a guide rail of a long square column shape having ball rolling grooves respectively opposing the ball rolling grooves of the nut so that the nut is movable in an axial direction through rolling of the balls.
However, in the prior art feed unit apparatus, since a dust seal is not satisfactory, there exists a problem in that when the feed unit apparatus is used in a welding robot, weld sputters are apt to enter the ball rolling surfaces resulting in malfunction, and when it is used in a clean room, lubrication grease tends to be scattered. Furthermore, a drawback is involved in that the assembling and adjustment of the feed unit apparatus is not so simple.